1. Field of the Invention
This invention relates to a recording and/or reproducing device for rotating a sheet-like disk such as floppy disk contained in a disk cassette for writing or reading information signals into or out of the disk.
2. Description of the Related Art
In The U.S. Pat. No. 4,445,155 owned by the present Applicant, there is shown and described a mounting structure for a disk driving electric motor for a recording and/or reproducing device for a micro floppy disk as shown in FIG. 1. The micro floppy disk 1 is comprised of a disk 4 having a center core 3 disposed centrally of the cassette 2. In the driving device 5, which mounts the micro floppy disk 1, the chassis 6 and the motor unit 7 on the chassis 6 are positioned and secured, and a chucking part 9 is provided for engaging with the center core 3 at the upper part of the spindle 8 which is the output shaft of the motor. The chucking part 9 is comprised of the driving pin 12 for positioning and driving the center core 3 by the turntable 10, through the medium of the lever 11 and a magnet 13 for attracting the center core 3. The center core 3 is provided with a driving pin 12 and an opening 14 for receiving the driving pin 12 and a center opening 15 for receiving the spindle 8 and adapted to be driven in engagement with the chucking part 9. A sheet 16 is affixed to that portion of the cassette 2 abutted by the spindle 8. The motor unit 7 is provided with a circuit board 17 for driving and controlling the motor. The chassis 6 has a positioning pin 18, the end part of which is engaged within a positioning aperture 19 in the lower surface of the cassette 2 for positioning the cassette 2 relative to the chassis 6. There is provided in the chassis 6 a motor unit positioning member 20 which is comprised of a motor height regulating surface 21 and a motor position regulating surface 22 for positioning the motor unit 7 relative to the inner surface of the cylindrical bore. The lower part of the motor unit 7 has a reference surface 23 contacting with the surface 21 and a cylindrical positioning section 24 introduced into the positioning surface 22. The unit is secured to the chassis 6 by screws 26 after positioning the motor unit 7 with respect to the chassis 6. In the prior-art driving unit, the motor unit 7 is separate from and mounted on the chassis 6 so that it has not been possible to construct the driving device with a mounting height smaller than the sum of the mounting height of the motor unit 7 and that of the chassis 6. Also, since the unit 7 and chassis 6 are separate units, it has been difficult to get the motor unit 7 positioned with respect to the chassis 6. Thus the use of a special jig and the use of skilled labor is required, if the mounting is performed only by screws. Deviation in the mounting position may be caused by impact or vibration. The positioning system shown in FIG. 1 has been suggested to overcome such drawback. In the positioning system shown in FIG. 1, mounting accuracy of the motor unit 7 on the chassis 6 is determined by the machining tolerance of the motor height regulating surface 21, reference surface 23, motor positioning surface 22 and the positioning portion 24. Mounting accuracy will be higher the longer the length L of the positioning portion 24. However, it is presently not possible to adopt a longer length L because of the demand for cost and size reduction of the driving unit. Thus it has become necessary to provide a motor mounting structure which has an overall combined height of the motor unit 7 and the chassis 6 as small as possible and which also lends itself to reduction of manufacturing costs.